Various automatic suction-type swimming pool cleaners have been developed in the past. For instance, U.S. Pat. No. 5,105,496 discloses a swimming pool cleaner having a primary fluid flow path, which extends from a primary inlet to a primary outlet, and a pair of secondary fluid flow paths, which extends from secondary inlets to secondary outlets. The swimming pool cleaner is also provided with a primary turbine mounted in the primary flow path for driving the swimming pool cleaner and a pair of secondary turbines mounted in the secondary flow path for steering the swimming pool cleaner. In addition, the swimming pool cleaner includes a suction nozzle having a throat, which extends from the primary inlet toward the primary turbine. As water flows into the primary flow path in response to the operation of an associated suction source (e.g., a pump) connected to the primary outlet, the suction nozzle functions to direct the water toward the primary turbine. As a result, the primary turbine is caused to rotate, thereby driving the swimming pool cleaner.
A special problem is presented when large objects flow into the suction nozzle during the operation of the swimming pool cleaner. More particularly, large objects become trapped in the throat of the suction nozzle, thereby obstructing same. Such an obstruction significantly restricts water flow through the throat of the suction nozzle, and, as a result, causes undue stress on the associated suction source and inefficient operation of the swimming pool cleaner.
U.S. Pat. No. 4,656,683 specifically addresses the foregoing problem by providing a suction cleaning apparatus with a suction nozzle which is made of a resiliently deformable material (e.g., silicone rubber) such that the suction nozzle can expand from a normal state to an expanded state in order to allow large objects to pass therethrough. However, because of the inherent resiliency of the deformable material, the suction nozzle tends to conform to the shape of large objects as they expand the suction nozzle, whereby the suction nozzle walls embrace the objects so as to impede their passage through the suction nozzle. As a result, some larger objects may actually become trapped in the suction nozzle, thereby causing an obstruction.